Battle! Clone trooper on AT-ST Prototype versus Separatist droid Hovertank. Image captured with flare lights.
The All Terrain Scout Transport (AT-ST) was a bipedal walker used by the Galactic Republic during the late Clone Wars and, later and more extensively, the Galactic Empire during the Galactic Civil War.
Colloquially known as a "chicken walker" because of its shape and walking motion, the AT-ST was a heavily armed light ground combat vehicle, and able to trek various environments. It was equipped with a chin-mounted double medium blaster cannon, a concussion grenade launcher on the starboard side of its head, 2 durasteel feet with claws, and a blaster cannon on the port side. It was designed to be a recon hit and run vehicle. It was lighter than its bigger brother the AT-AT walker and could withstand standard blaster fire, but was vulnerable to heavy laser fire and missiles as well as physical attacks to the legs and the side of the head, as seen by the Ewoks destroying AT-ST's by logs ramming the sides of the heads. They also could be forced into by species with great physical strength, like a Wookiee; as seen by Chewbacca forcing his way through the top hatch and taking control of the walker. Properly thrown grenades could be thrown into the window hatches, as well.
The chin guns had an effective range of two kilometers and were used for anti-vehicle attacks, while the blaster cannon and grenade launcher provided close-range protection against infantry and light emplacements. AT-STs were piloted by a crew of two drivers.
The bipedal propulsion system was one of the primary weaknesses of the AT-ST. While on even terrain the walker could achieve over 90 kilometers per hour, but on uneven or shifting terrain a walker could quickly become unbalanced enough to fall over.
Early on in the Clone Wars, engineers at Rothana were busy developing a new bipedal walker, known as the All Terrain Scout Transport, following their construction and testing of the AT-XT. The AT-XT enjoyed moderate success during its somewhat brief operational time, but was rarely used during the war. At the end of the war the CIS constructed some of these weapons on the planet of Diado this production was stopped after Saesee Tiin destroyed the factory.
The earliest models would be deployed by the Grand Army of the Republic during the latter stages of the Clone Wars. The conflict would also see the debut of several other bipedal walker designs, like the AT-RT.
Under the Empire, Balmorra was the center of AT-ST production. The AT-ST was later viewed by Imperial commanders as a highly versatile weapon, excelling against infantry and lightly armored vehicles, but also useful for protecting vital units and patrolling hostile areas.
AT-STs were used by Blizzard Force during the Battle of Hoth. The Blizzard Force AT-ST was especially modified for polar climates, as were all the vehicles used on Hoth. It was equipped with ground penetrating sensor equipment that could detect instabilities in the permafrost and relay information back to the heavier vehicles, thus ensuring they avoided unstable ground. The walkers had a unit insignia consisting of a horned helmet. In the Battle of Endor, AT-STs were deployed by the Empire against the Rebel and Ewok ground troops. The walkers were very effective against these troops, until many of them were destroyed by Ewok traps and another AT-ST hijacked by Chewbacca with the help of some Ewoks.
The AT-ST's problem with shifting terrain, despite the designation 'All-Terrain', was demonstrated during the Battle of Endor, when Ewoks released a large pile of logs and stones to roll down the hill into the path of an AT-ST. The walker was unable to handle the rapidly shifting ground, and despite attempts by the pilot to stabilize the vehicle, it fell on its side and was destroyed. The Ewoks also used strategically-positioned logs hanging from trees to eliminate several other walkers.
The Imperial Remnant would go on to use AT-STs, though not as extensively.

About this creation

Actual battlefield light conditions as the planet rotates very fast. It was dusk already but the combatants are still at it.
AT-ST Prototype in profile.
Hovertank in profile.
Close-up of the AT-ST cockpit. Notice the weapon emplacements that would soon be replicated on all AT-STs.
Looks like the Clonetrooper won and disembarked the one-man walker.
Aftermath of the battlefield. Is that a Classic Space brick I see there. Colony must have been an outpost for the bygone LegoSpacy Inc. in the early days of space travel.
Thanks to Brickmaster, I can build to my heart's content my own StarWars stories.
Rifle blaster, standard heavy-sidearms of Republic troopers.